Synchronized pitch and timing cues in a hearing prosthesis system

ABSTRACT

Presented herein are binaural hearing prosthesis systems that are configured to provide a recipient with pitch cues at both ears, while preserving/retaining binaural timing cues.

BACKGROUND Field of the Invention

The present invention relates generally to hearing prosthesis systems.

Related Art

Medical devices have provided a wide range of therapeutic benefits torecipients over recent decades. Medical devices can include internal orimplantable components/devices, external or wearable components/devices,or combinations thereof (e.g., a device having an external componentcommunicating with an implantable component). Medical devices, such astraditional hearing aids, partially or fully-implantable hearingprostheses (e.g., bone conduction devices, mechanical stimulators,cochlear implants, etc.), pacemakers, defibrillators, functionalelectrical stimulation devices, and other medical devices, have beensuccessful in performing lifesaving and/or lifestyle enhancementfunctions and/or recipient monitoring for a number of years.

The types of medical devices and the ranges of functions performedthereby have increased over the years. For example, many medicaldevices, sometimes referred to as “implantable medical devices,” nowoften include one or more instruments, apparatus, sensors, processors,controllers or other functional mechanical or electrical components thatare permanently or temporarily implanted in a recipient. Thesefunctional devices are typically used to diagnose, prevent, monitor,treat, or manage a disease/injury or symptom thereof, or to investigate,replace or modify the anatomy or a physiological process. Many of thesefunctional devices utilize power and/or data received from externaldevices that are part of, or operate in conjunction with, implantablecomponents.

SUMMARY

In one aspect presented herein, a method is provided. The methodcomprises: receiving a first set of sound signals at a first cochlearimplant of a bilateral cochlear implant system; receiving a second setof sound signals at a second cochlear implant of the bilateral cochlearimplant system, wherein the first set of sound signals and the secondset of sound signals are associated with a same one or more soundsources; generating, at the first cochlear implant, a first sequence ofstimulation pulses based on the first set of sound signals, wherein thefirst sequence of stimulation pulses have amplitudes that are modulatedwith a first modulation; delivering the first sequence of stimulationpulses to a first ear of a recipient of the bilateral cochlear implantsystem; generating, at the second cochlear implant, a second sequence ofstimulation pulses based on the second set of sound signals, wherein thesecond sequence of stimulation pulses have amplitudes that are modulatedusing the same first modulation as the first sequence of stimulationpulses; and delivering the second sequence of stimulation pulses to asecond ear of the recipient, wherein the second sequence of stimulationpulses is delivered to the recipient with a time delay relative todelivery of the first sequence of stimulation pulses and wherein thetime delay is based on an Interaural Time Difference (ITD) associatedwith receipt of the first set of sound signals at the first cochlearimplant and receipt of the second set of sound signals at the secondcochlear implant.

In another aspect, a cochlear implant system is provided. The cochlearimplant system comprises: a first cochlear implant configured to:receive a first set of sound signals associated with at least one soundsource, convert the first set of sound signals into a first stimulationpulse train, wherein the first stimulation pulse train is artificiallyamplitude modulated based on a fundamental frequency associated with theat least one sound source, and deliver the first stimulation pulse trainto a first ear of a recipient of the cochlear implant system; and asecond cochlear implant configured to: receive a second set of soundsignals associated with the at least one sound source, convert thesecond set of sound signals into a second stimulation pulse train,wherein the second stimulation pulse train is artificially amplitudemodulated based on the fundamental frequency associated with the atleast one sound source, and deliver the second stimulation pulse trainto a second ear of the recipient with a time delay relative to deliveryof the first stimulation pulse train to a first ear of a recipient.

In another aspect, a method is provided. The method comprises: receivinga first set of sound signals at a first cochlear implant of a bilateralcochlear implant system; receiving a second set of sound signals at asecond cochlear implant of the bilateral cochlear implant system,wherein the first set of sound signals and the second set of soundsignals are associated with a same one or more sound sources;generating, at the first cochlear implant, a first sequence ofstimulation pulses based on the first set of sound signals, wherein thefirst sequence of stimulation pulses have amplitudes that are modulatedwith a first modulation; delivering the first sequence of stimulationpulses to a first ear of a recipient of the bilateral cochlear implantsystem; generating, at the second cochlear implant, a second sequence ofstimulation pulses based on the second set of sound signals, wherein thesecond sequence of stimulation pulses have amplitudes that are modulatedusing the same first modulation as the first sequence of stimulationpulses; and delivering the second sequence of stimulation pulses to asecond ear of the recipient, wherein the second sequence of stimulationpulses is delivered to the recipient with a time delay relative todelivery of the first sequence of stimulation pulses and wherein thetime delay is based on an Interaural Time Difference (ITD) associatedwith receipt of the first set of sound signals at the first cochlearimplant and receipt of the second set of sound signals at the secondcochlear implant.

In another aspect, a cochlear implant system is provided. The cochlearimplant system comprises: a first cochlear implant configured to:receive a first set of sound signals generated by at least one soundsource, convert the first set of sound signals into a first stimulationpulse train, wherein the first stimulation pulse train is artificiallyamplitude modulated based on a fundamental frequency associated with theat least one sound source, and deliver the first stimulation pulse trainto a first ear of a recipient of the cochlear implant system; and asecond cochlear implant configured to: receive a second set of soundsignals generated by the at least one sound source, convert the secondset of sound signals into a second stimulation pulse train, wherein thesecond stimulation pulse train is artificially amplitude modulated basedon the fundamental frequency associated with the at least one soundsource, determine, relative to delivery of the first stimulation pulsetrain to the first ear of the recipient, a time delay for delivery ofthe second stimulation pulse train to a second ear of the recipient, anddeliver the second stimulation pulse train to the second ear of therecipient at a time corresponding to the time delay.

In another aspect, non-transitory computer readable storage mediaencoded with instructions are provided. The instructions, when executedby one or more processors, cause the one or more processors to:generate, at a first cochlear implant of a cochlear implant system, afirst sequence of stimulation pulses representative of first audio datareceived at the first cochlear implant; modulate the first sequence ofstimulation pulses based on one or more features of the first audio dataand the second audio data; generate, at a second cochlear implant of thecochlear implant system, a second sequence of stimulation pulsesrepresentative of second audio data received at the second cochlearimplant; and modulate the second sequence of stimulation pulses based onthe one or more features of the first audio data and the second audiodata.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described herein in conjunctionwith the accompanying drawings, in which:

FIG. 1A is a schematic view of a cochlear implant system in whichembodiments presented herein may be implemented;

FIG. 1B is a side view of a recipient wearing the cochlear implantsystem of FIG. 1A;

FIG. 1C is a schematic view of the components of the cochlear implantsystem of FIG. 1A;

FIGS. 1D and 1E are block diagrams of sound processing units formingpart of the cochlear implant system of FIG. 1A;

FIG. 2 is a functional block diagram of a cochlear implant system, inaccordance with certain embodiments presented herein;

FIG. 3 is a schematic diagram illustrating stimulation pulse timing of acochlear implant system, in accordance with certain embodimentspresented herein;

FIG. 4 is a functional block diagram of another cochlear implant system,in accordance with certain embodiments presented herein;

FIG. 5 is a functional block diagram of another cochlear implant system,in accordance with certain embodiments presented herein;

FIG. 6A is a functional block diagram of an audio synchronizer of acochlear implant system, in accordance with certain embodimentspresented herein;

FIG. 6B is a functional block diagram of another audio synchronizer of acochlear implant system, in accordance with certain embodimentspresented herein;

FIG. 6C is a functional block diagram of another audio synchronizer of acochlear implant system, in accordance with certain embodimentspresented herein;

FIG. 7 is a flowchart of a method, in accordance with certainembodiments presented herein; and

FIG. 8 is a flowchart of another method, in accordance with certainembodiments presented herein.

DETAILED DESCRIPTION

Medical devices and medical device systems (e.g., including multipleimplantable medical devices) have provided a wide range of therapeuticbenefits to recipients over recent decades. For example, a hearingprosthesis system is a type of implantable medical device system thatincludes one or more hearing prostheses that operate to convert soundsignals into one or more acoustic, mechanical, and/or electricalstimulation signals for delivery to a recipient. The one or more hearingprostheses that can form part of a hearing prosthesis system include,for example, hearing aids, cochlear implants, middle ear stimulators,bone conduction devices, brain stem implants, electro-acoustic cochlearimplants or electro-acoustic devices, and other devices providingacoustic, mechanical, and/or electrical stimulation to a recipient.

One specific type of hearing prosthesis system, referred to herein as a“binaural hearing prosthesis system” or more simply as a “binauralsystem,” includes two hearing prostheses, where one of the two hearingprosthesis is positioned at each ear of the recipient. Morespecifically, in a binaural system each of the two prostheses providesstimulation to one of the two ears of the recipient (i.e., either theright or the left ear of the recipient).

Presented herein are binaural hearing prosthesis systems, such asbinaural or bilateral cochlear implant systems, that are configured toprovide a recipient with pitch cues at both ears, whilepreserving/retaining binaural timing cues. More specifically, a binauralor bilateral cochlear implant system comprises first and second cochlearimplants positioned at first and second ears, respectively, of arecipient. The first cochlear implant is configured to capture/receive afirst set of sound signals and convert the first set of sound signalsinto a first stimulation pulse sequence for delivery to the first ear ofthe recipient. Similarly, the second cochlear implant is configured toreceive a second set of sound signals and convert the second set ofsound signals into a second stimulation pulse sequence for delivery tothe second ear of the recipient. Each of the first and secondstimulation pulse sequences are amplitude modulated based on thefundamental frequency (F0) of the first and second sets sound signals,which are associated with a same one or more sound sources, therebyproviding the recipient with a pitch cue.

Additionally, the first and second sets of sound signals will bereceived at the first and second cochlear implants with a relativetiming that corresponds to a relative location of the one or more soundsources. The first and second cochlear implants are configured tosynchronize delivery of the first sequence of stimulation pulses to afirst ear of the recipient with delivery of the second sequence ofstimulation pulses to a second ear of the recipient based on therelative timing, thereby providing the recipient with a binaural timingcue.

It is to be appreciated that the techniques presented herein mayimplemented with any of a number of medical devices and systems,including in conjunction with cochlear implants or other auditoryprostheses, balance prostheses (e.g., vestibular implants), retinal orother visual prostheses, cardiac devices (e.g., implantable pacemakers,defibrillators, etc.), seizure devices, sleep apnea devices,electroporation devices, spinal cord stimulators, deep brainstimulators, motor cortex stimulators, sacral nerve stimulators,pudendal nerve stimulators, vagus/vagal nerve stimulators, trigeminalnerve stimulators, diaphragm (phrenic) pacers, pain relief stimulators,other neural, neuromuscular, or functional stimulators, etc. However,merely for ease of description, aspects of the techniques will begenerally described with reference to a specific medical device system,namely a bilateral cochlear implant systems. As used herein, a“bilateral” cochlear implant system is a system that includes first andsecond cochlear implants located at first and second ears, respectively,of a recipient. In such systems, each of the two cochlear implant systemdelivers stimulation (current) pulses to one of the two ears of therecipient (i.e., either the right or the left ear of the recipient). Ina bilateral cochlear implant system, one or more of the two cochlearimplants may also deliver acoustic stimulation to the ears of therecipient (e.g., an electro-acoustic cochlear implant) and/or the twocochlear implants need not be identical with respect to, for example,the number of electrodes used to electrically stimulate the cochlea, thetype of stimulation delivered, etc.

FIGS. 1A-1E are diagrams illustrating one example bilateral cochlearimplant system 100 configured to implement the techniques presentedherein. More specifically, FIGS. 1A-1E illustrate an example bilateralsystem 100 comprising left and right cochlear implants, referred to ascochlear implant 102L and cochlear implant 102R. FIGS. 1A and 1B areschematic drawings of a recipient wearing the left cochlear implant 102Lat a left ear 141L and the right cochlear implant 102R at a right ear141R, while FIG. 1C is a schematic view of each of the left and rightcochlear implants. FIGS. 1D and 1E are block diagrams illustratingfurther details of the left cochlear implant 102L and the right cochlearimplant 102R, respectively.

Referring specifically to FIG. 1C, cochlear implant 102L includes anexternal component 104L that is configured to be directly or indirectlyattached to the body of the recipient and an implantable component 112Lconfigured to be implanted in the recipient. The external component 104Lcomprises a sound processing unit 106L, while the implantable component112L includes an internal coil 114L, a stimulator unit 142L and anelongate stimulating assembly (electrode array) 116L implanted in therecipient's left cochlea (not shown in FIG. 1C).

The cochlear implant 102R is substantially similar to cochlear implant102L. In particular, cochlear implant 102R includes an externalcomponent 104R comprising a sound processing unit 106R, and animplantable component 112R comprising internal coil 114R, stimulatorunit 142R, and elongate stimulating assembly 116R.

FIG. 1D is a block diagram illustrating further details of cochlearimplant 102L, while FIG. 1E is a block diagram illustrating furtherdetails of cochlear implant 102R. As noted, cochlear implant 102R issubstantially similar to cochlear implant 102L and includes likeelements as that described below with reference to cochlear implant102L. For ease of description, further details of cochlear implant 102Rhave been omitted from the description.

As noted, the external component 104L of cochlear implant 102L includesa sound processing unit 106L. The sound processing unit 106L comprisesone or more input devices 113L that are configured to receive inputsignals (e.g., sound or data signals). In the example of FIG. 1D, theone or more input devices 113L include one or more sound input devices118L (e.g., microphones, audio input ports, telecoils, etc.), one ormore auxiliary input devices 119L (e.g., audio ports, such as a DirectAudio Input (DAI), data ports, such as a Universal Serial Bus (USB)port, cable port, etc.), and a wireless transmitter/receiver(transceiver) 120L. However, it is to be appreciated that one or moreinput devices 113L may include additional types of input devices and/orless input devices (e.g., the wireless transceiver 120L and/or one ormore auxiliary input devices 119L could be omitted).

The sound processing unit 106L also comprises one type of aclosely-coupled transmitter/receiver (transceiver) 122L, referred to asor radio-frequency (RF) transceiver 122L, a power source 123L, and aprocessing module 124L. The processing module 124L comprises one or moreprocessors 125L and a memory 126L that includes binaural soundprocessing logic 128L. In the examples of FIGS. 1A-1E, the soundprocessing unit 106L and the sound processing unit 106R are off-the-ear(OTE) sound processing units (i.e., components having a generallycylindrical shape and which is configured to be magnetically coupled tothe recipient's head), etc. However, it is to be appreciated thatembodiments of the present invention may be implemented by soundprocessing units having other arrangements, such as by a behind-the-ear(BTE) sound processing unit configured to be attached to and wornadjacent to the recipient's ear, including a mini or micro-BTE unit, anin-the-canal unit that is configured to be located in the recipient'sear canal, a body-worn sound processing unit, etc.

The implantable component 112L comprises an implant body (main module)134L, a lead region 136L, and the intra-cochlear stimulating assembly116L, all configured to be implanted under the skin/tissue (tissue) 115of the recipient. The implant body 134L generally comprises ahermetically-sealed housing 138L in which RF interface circuitry 140Land a stimulator unit 142L are disposed. The implant body 134L alsoincludes the internal/implantable coil 114L that is generally externalto the housing 138L, but which is connected to the transceiver 140L viaa hermetic feedthrough (not shown in FIG. 1D).

As noted, stimulating assembly 116L is configured to be at leastpartially implanted in the recipient's cochlea. Stimulating assembly116L includes a plurality of longitudinally spaced intra-cochlearelectrical stimulating contacts (electrodes) 144L that collectively forma contact or electrode array 146L for delivery of electrical stimulation(current) to the recipient's cochlea.

Stimulating assembly 116L extends through an opening in the recipient'scochlea (e.g., cochleostomy, the round window, etc.) and has a proximalend connected to stimulator unit 142L via lead region 136L and ahermetic feedthrough (not shown in FIG. 1D). Lead region 136L includes aplurality of conductors (wires) that electrically couple the electrodes144L to the stimulator unit 142L.

As noted, the cochlear implant 102L includes the external coil 108L andthe implantable coil 114L. The coils 108L and 114L are typically wireantenna coils each comprised of multiple turns of electrically insulatedsingle-strand or multi-strand platinum or gold wire. Generally, a magnetis fixed relative to each of the external coil 108L and the implantablecoil 114L. The magnets fixed relative to the external coil 108L and theimplantable coil 114L facilitate the operational alignment of theexternal coil 108L with the implantable coil 114L. This operationalalignment of the coils enables the external component 104L to transmitdata, as well as possibly power, to the implantable component 112L via aclosely-coupled wireless link formed between the external coil 108L withthe implantable coil 114L. In certain examples, the closely-coupledwireless link is a radio frequency (RF) link. However, various othertypes of energy transfer, such as infrared (IR), electromagnetic,capacitive and inductive transfer, may be used to transfer the powerand/or data from an external component to an implantable component and,as such, FIG. 1D illustrates only one example arrangement.

As noted above, sound processing unit 206L includes the processingmodule 124L. The processing module 124L is configured to convertreceived input signals (received at one or more of the input devices113L) into output signals 145L for use in stimulating a first ear of arecipient (i.e., the processing module 124L is configured to performsound processing on input signals received at the sound processing unit106L). Stated differently, in the sound processing mode, the one or moreprocessors 125L are configured to execute binaural sound processinglogic 128L in memory 126L to convert the received input signals intooutput signals 145L that represent electrical stimulation for deliveryto the recipient.

In the embodiment of FIG. 1D, the output signals 145L are provided tothe RF transceiver 114, which transcutaneously transfers the outputsignals 145L (e.g., in an encoded manner) to the implantable component112L via external coil 108L and implantable coil 114L. That is, theoutput signals 145L are received at the RF interface circuitry 140L viaimplantable coil 114L and provided to the stimulator unit 142L. Thestimulator unit 142L is configured to utilize the output signals 145L togenerate electrical stimulation signals (e.g., current signals) fordelivery to the recipient's cochlea via one or more stimulating contacts144L. In this way, cochlear implant 102L electrically stimulates therecipient's auditory nerve cells, bypassing absent or defective haircells that normally transduce acoustic vibrations into neural activity,in a manner that causes the recipient to perceive one or more componentsof the received sound signals.

As noted, cochlear implant 102R is substantially similar to cochlearimplant 102L and comprises external component 104R and implantablecomponent 112R. External component 104R includes a sound processing unit106R that comprises external coil 108R, input devices 113R (i.e., one ormore sound input devices 118R, one or more auxiliary input devices 119R,and wireless transceiver 120R), closely-coupled transceiver (RFtransceiver) 122R, power source 123R, and processing module 124R. Theprocessing module 124R includes one or more processors 125R and a memory126R that includes binaural sound processing logic 128R. The implantablecomponent 112R includes an implant body (main module) 134R, a leadregion 136R, and the intra-cochlear stimulating assembly 116R, allconfigured to be implanted under the skin/tissue (tissue) 115 of therecipient. The implant body 134R generally comprises ahermetically-sealed housing 138R in which RF interface circuitry 140Land a stimulator unit 142R are disposed. The implant body 134R alsoincludes the internal/implantable coil 114R that is generally externalto the housing 138R, but which is connected to the RF interfacecircuitry 140R via a hermetic feedthrough (not shown in FIG. 1E). Thestimulating assembly 116R includes a plurality of longitudinally spacedintra-cochlear electrical stimulating contacts (electrodes) 144R thatcollectively form a contact or electrode array 146R for delivery ofelectrical stimulation (current) to the recipient's cochlea. Each of theelements of cochlear implant 102R shown in FIG. 1E are similar tolike-numbered elements of cochlear implant 102L shown in FIG. 1D.

In normal hearing, the main binaural cues for left/right soundlocalization are the Interaural (Inter-aural) Level Difference (ILD) andthe Interaural (Inter-aural) Time Difference (ITD). A primary benefit ofa bilateral cochlear implant system is that such systems can provide arecipient with ILD (inter-aural level difference) cues. However,existing bilateral cochlear implant systems do not provide recipientswith correct ITD cues.

Presented herein are techniques that enable a bilateral cochlear implantsystem to provide a recipient with pitch cues (stimulation pulsesequence amplitude modulation) in a manner that does not disturb the ITDcues (i.e., enable a recipient to benefit from both pitch cues andbinaural timing cues). More specifically, in the example of FIGS. 1A-1E,the cochlear implant 102L is configured to receive first set of soundsignals and convert the first set of sound signals into a firststimulation pulse sequence for delivery to the first ear of therecipient. Similarly, the cochlear implant 102R is configured to receivea second set of sound signals and convert the second set of soundsignals into a second stimulation pulse sequence for delivery to thesecond ear of the recipient. The first and second stimulation pulsesequences generated by cochlear implants 102L and 102R, respectively,are amplitude modulated based on the fundamental frequency (F0) of thefirst and second sets sound signals (which are associated with a sameone or more sound sources). That is, the modulation of the stimulationpulse amplitudes in the first and second pulse sequences is synchronizedacross both the left and right sides, and is based on the fundamentalfrequency of received sound signals

Additionally, the first and second sets of sound signals will bereceived at the cochlear implants 102L and 102R with a relative timingthat corresponds to a relative location of the one or more soundsources. That is, cochlear implants 102L and 102R are configured tosynchronize delivery of the first sequence of stimulation pulses to afirst ear of the recipient with delivery of the second sequence ofstimulation pulses to a second ear of the recipient based on therelative location of the sound sources that generated the first andsecond sets of sound signals. As a result, bilateral cochlear implantsystem 100 is configured to both improve pitch perception and provideappropriate ITD cues.

FIG. 2 is a functional block diagram of a bilateral cochlear implantsystem 200 in accordance with embodiments presented herein. As shown,the bilateral cochlear implant system 200 comprises a left (first)cochlear implant 202L and a right (second) cochlear implant 202R.Referring first to cochlear implant 202L, the cochlear implant comprisesa microphone array 250L (e.g., dual-microphone system), a filterbank252L, a smoother 254L, a mixer 256L, a pulse generator 258L, and amodulation controller 260L.

In certain examples, the operations described below with reference tofilterbank 252L, smoother 254L, mixer 256L, and modulation controller260L may be performed at a processing module, such as processing module124L of FIG. 1D. Additionally, in certain examples, certain operationsdescribed below with reference to pulse generator 258L may be performedat a processing module (e.g., processing module 124L), while otheroperations may be performed at a stimulator unit, such as stimulatorunit 142L of FIG. 1D.

Cochlear implant 202R, which is substantially similar to cochlearimplant 202L, comprises a microphone array 250R, a filterbank 252R, asmoother 254R, a mixer 256R, a pulse generator 258R, and a modulationcontroller 260R. In certain examples, the operations described belowwith reference to filterbank 252R, smoother 254R, mixer 256R, andmodulation controller 260R may be performed at a processing module, suchas processing module 124R of FIG. 1E. Additionally, in certain examples,certain operations described below with reference to pulse generator258R may be performed at a processing module (e.g., processing module124R), while other operations may be performed at a stimulator unit,such as stimulator unit 142R of FIG. 1E.

Although FIG. 2 will be described with reference to the use ofmicrophone arrays 250L and 250R, it is to be appreciated that thecochlear implants 202L and 202R may also or alternatively includedifferent types and combinations of sound input devices. It is also tobe appreciated that the functional blocks shown in FIG. 2 for each ofcochlear implants 202L and 202 may be distributed across one, two, ormore different physical devices. For example, certain functional blocksshown in FIG. 2 for cochlear implant 202L may be part of an externalcomponent (e.g., external component 104L), while other functional blocksfor cochlear implant 202L may be part of an implantable component (e.g.,implantable component 112L).

Alternatively, all of the functional blocks for cochlear implant 202Lmay be part of an implantable component, the functional blocks forcochlear implant 202L may be split between two external components andan implantable component, etc.

Returning to the example of FIG. 2, a first set of acoustic soundsignals (sounds) 248L are received at the microphone array 250L and areused to generate audio data (aL) 251L. More specifically, the audio data251L is derived from microphone signals, processed by analog-to-digitalconverters (ADC), a beamformer, and an Automatic Gain Control (AGC), allof which have been omitted from FIG. 2 for ease of illustration. In asimilar manner, microphone array 250R converts a second set of acousticsound signals (sounds) 248R are into audio data (aR) 251R.

Due to the tonotopic mapping of a recipient's cochlea, differentportions of the received sound signals 248L and 248R are delivered todifferent target locations/places in the cochlear via different“stimulation channels.” As used herein, a stimulation channel is acombination/set of implanted electrodes that are usedsimultaneously/collectively to deliver current signals to the cochlea soas to elicit stimulation at a specific target location/place of thecochlea. Due, in part, to the use of different stimulation channels todeliver stimulation to the recipient, the audio data 251L and 251R isapplied to the filterbanks 252L and 252R, respectively. The filterbanks252L and 252R each comprise a band-pass filter and an envelope detectorfor each of a plurality of stimulation channels. As such, the filterbank252L produces a set (e.g., a plurality) of filterbank envelopes 253L(v1L) and filterbank 252R produces a set of filterbank envelopes 253R(v1R), where each filterbank envelope is associated with a stimulationchannel.

In FIG. 2, the lines/arrows marked by “/N,” such as arrows 253L and253R, indicate sets of related signals, with one signal for each of aplurality of stimulation channels in the cochlear implant system. Atypical cochlear implant system may have between 12 and 22 stimulationchannels, although other numbers of channels may be used in differentembodiments.

The filterbank envelopes 253L and 253R are applied to the smoothers 254Land 254R, respectively, which smooth each of the filterbank envelopes toremove amplitude fluctuations having frequencies within and above anexpected range of fundamental frequencies (e.g., 70 Hertz (Hz) andhigher). The smoothers 254L and 254R produce a set of smoothed envelopesignals 255L (v3L) and 255R (v3R), respectively.

Additionally, the smoothers 254L and 254R delay the sets of filterbankenvelopes 253L and 253R, respectively, to produce a set of delayedfilterbank envelopes 257L (v2L) and 257R (v2R), respectively, each witha delay that matches the inherent delay that is introduced by thesmoothing operation of smoothers 254L and 254R, respectively. In otherwords, envelopes 255L and 257L are aligned in time and the envelopes255R and 257R are aligned in time.

As noted elsewhere herein, the first set of acoustic sound signals 248Land the second set of acoustic sound signals 248R are generated by thesame one or more sound sources 221. As such, the set of acoustic soundsignals 248L and the second set of acoustic sound signals 248R arereceived “contemporaneously” (i.e., around the same time) by thecochlear implants 202L and 202R. However, the first set of acousticsound signals 248L and the second set of acoustic sound signals 248R arereceived at the respective cochlear implants 202L and 202R with arelative timing that corresponds to the location of the one or moresound sources 221. In other words, one of either the first or second setof acoustic sound signals may be received with a delay, relative to thereceipt of the other of first or second set of acoustic sound signals.The delay corresponds to the Interaural Time Difference (ITD) betweenthe left and right ears of the recipient, relative to the location ofthe one or more sound sources. The ITD may change (increase or decrease)as the location of the one or more sound sources 211 changes.

In the example of FIG. 2, cochlear implants 202L and 202R are configuredto operate a two-way audio link/channel 262 that enables the transferof, for example, audio data 251L and 251R between the cochlear implants.That is, the two-way audio channel 262 enables the cochlear implant 202Rto send audio data 251R (i.e., send data representing the second set ofsound signals 248R) to cochlear implant 202L and, similarly, enablescochlear implant 202L to send audio data 251L (e., send datarepresenting the first set of sound signals 248L) to cochlear implant202R. Therefore, cochlear implants 202L and 202R each have access toboth of the audio data 251L and 251R and, accordingly, both sets ofsound signals 248L and 248R. The two-way audio channel 262 may be awired electrical channel or a wireless channel (e.g., a standardizedwireless channel, such as Bluetooth®, Bluetooth® Low Energy (BLE) orother channel interface making use of any number of standard wirelessstreaming protocols; a proprietary protocol for wireless streaming ofthe audio data; etc. Bluetooth® is a registered trademark owned by theBluetooth® SIG).

In the example of FIG. 2, the audio data 251L and the audio data 251R(either received directly or received via the two-way audio channel 262)are applied to both of the modulation controllers 260L and 260R. Ingeneral, the modulation controllers 260L and 260R are configured togenerate a modulator signal 259L (mL) and 259R (mR), respectively, thateach have a period corresponding to the fundamental frequency (F0) ofthe most dominant harmonic component in the audio data 251L and 251R.That is, the modulation controllers 260L and 260R are each configured toidentify the fundamental frequency (F0) associated with received soundsignals 248L and 248R. The modulation controllers 260L and 260R thengenerate the modulation signals 259L and 259R based on the identifiedfundamental frequency (F0).

In the example of FIG. 2, the modulation controllers 260L and 260Roperate on both the ipsilateral (same side) audio data 251L and thecontralateral (other side) audio data 251R. In certain embodiments,modulation controller 260L is configured to generate a first estimate ofthe fundamental frequency, referred to as “F0 _(iL),” using theipsilateral audio data 251L and a second estimate of the fundamentalfrequency, referred to as “F0 _(cL)” using the contralateral audio 251R.If the two estimates F0 _(iL), and F0 _(cL) are approximately equal,then it is assumed that there is one dominant sound source in theenvironment, and binaural processing functions in accordance withembodiments presented are enabled. Conversely, if the two estimates F0_(iL), and F0 _(cL) are significantly different, then it is assumed thatthere is not a single dominant sound source, and the binaural processingfunctions in accordance with embodiments presented herein may bedisabled. The modulation controller 260R may operate in a similar tomanner to generate and compare two estimates of the fundamentalfrequency, referred to as “F0 _(iR)” (made using the ipsilateral audiodata 251R) and F0 _(cR)” (made using the contralateral audio 251L).

The binaural processing functions in accordance with embodimentspresented herein may be disabled when, for example, there is one speakerclose to the left ear, and a different speaker close to the right ear.In another example, the binaural processing functions in accordance withembodiments presented herein may be disabled when the recipient isholding a telephone to one ear, while the other ear is exposed toambient sounds. In this case, the binaural processing functions aredisabled so that the cochlear implants 202L and 202R operateindependently.

When not disabled, several binaural processing functions in accordancewith embodiments presented herein may be applied by the cochlear implant202L and cochlear implant 202R. Referring first to cochlear implant202L, a first binaural processing function in accordance withembodiments presented herein is that the two F0 estimates F0 _(iL) andF0 _(cL) are combined into a single joint estimate, referred to as “F0_(jL).” This joint estimate F0 _(jL) is then used to generate themodulation signal 259L. At 264L, the modulation signal 259L is used tomodulate the smoothed envelope signals 255L, producing modulatedenvelope signals 261L (v4L).

Cochlear implant 202R operates in a similar manner to combine the two F0estimates F0 _(iR) and F0 _(cR) into a single joint estimate, referredto as “F0 _(jR),” which is then used to generate the modulation signal259R. The modulation signal 259R is used to modulate the smoothedenvelope signals 255R, producing modulated envelope signals 261R (v4R).

In addition to generating modulator signals 259L and 259R, themodulation controllers 260L and 260R are each configured to generate anestimate, for each of the plurality of band-pass filter channels, of theprobability that the signal component in the corresponding band-passfilter channel is harmonically related to the dominant harmoniccomponent in the audio data 251L and 251R. As such, the modulationcontroller 260L generates a set 263L of harmonic probability signals(hL) and modulation controller 260R generates a set 263R of harmonicprobability signals (hR). Each signal in the sets 263L and 263Rcorresponds to one of the band-pass filter channels and provides anestimate of the probability that the signal in that correspondingband-pass filter channel is harmonically related to the dominantharmonic component in audio data 251L and 251R.

The sets 263L and 263R of harmonic probability signals are applied tothe mixers 256L and 256R, respectively. The mixer 256L is configured tosum the delayed filterbank envelopes 257L (v2L) and the modulatedenvelope signals 261L (v4L), with the relative proportions of eachcontrolled by the harmonic probability signals in set 261L. The mixer256L produces a set 265L of modulated output envelopes (v5L). The set265L of modulated output envelopes are then applied to the pulsegenerator 258L. Mixer 256R operates in a similar manner to sum thedelayed filterbank envelopes 257R (v2R) and the modulated envelopesignals 261R (v4R), with the relative proportions of each controlled bythe harmonic probability signals in set 261R. The mixer 256R produces aset 265R of modulated output envelopes (v5R). The set 265R of modulatedoutput envelopes are then applied to the pulse generator 258R.

A second binaural processing function at cochlear implants 202L and 202Eis implemented by an Interaural Time Difference (ITD) estimators 266Land 266R of the modulation controllers 260L and 260R, respectively,which determine the ITD of the most dominant harmonic component in audiodata 251L and 251R. The ITD estimate generated by the ITD estimator 266Lcontrols the delay signal 267L (tL), while the ITD estimate generated bythe ITD estimator 266R controls the delay signal 267R (tR). Morespecifically, if the most dominant harmonic sound source is on the leftside of the recipient's head (i.e., proximate to cochlear implant 202L),then the delay signal 267L will be zero, and delay signal 267R willrepresent the time delay required for the sounds from the most dominantharmonic sound source to reach the right ear. However, if the dominantharmonic sound source is on the right side of the recipient's head(i.e., proximate to cochlear implant 202R), then the delay signal 267Rwill be zero, and the delay signal 267L will represent the time delayrequired for the sounds from the most dominant harmonic sound source toreach the left ear. If the dominant harmonic sound source is directly infront of the recipient, then both delay signals 267L and 267R will bezero, as there is no ITD between the left and right ears for a soundsource directly in front of the recipient. If the binaural processingfunctions are disabled, then no ITD estimate is made and delay signals267L and 267R will also be zero.

Delay signals 267L and 267R are applied to the pulse generators 258L and258R, respectively. As noted above, the set 265L of output envelopes(v5L) are also applied to the pulse generator 258L, while the set 265Rof output envelopes (v5R) are also applied to the pulse generator 258R.The pulse generator 258L is configured to sample the set 265L of outputenvelopes (v5L) to produce a stimulation pulse sequence 268L (i.e., asequence of stimulation pulses (pL)). Similarly, pulse generator 258R isconfigured to sample the set 265R of output envelopes (v5R) to produce astimulation pulse sequence 268R (pL). In the example of FIG. 2, thepulses with one of the stimulation pulse sequences 268L or 268R aredelayed by a time interval controlled by the delay signals 267L or 267R,(i.e., the pulses are generated with a time delay that is based on theITD estimate made by modulation controllers 260L and 260R).

FIG. 3 is a diagram illustrating one example stimulation pulse sequence268L and an example stimulation pulse sequence 268R generated bycochlear implants 202L and 202R, respectively, in accordance withembodiments presented herein. For ease of illustration and clarity, onlyfour channels are shown. However, as noted above, a typical cochlearimplant system may have anywhere from 12 to 22 channels, although othernumbers of channels are possible. In FIG. 3, the channel stimulationrate is 1000 pulses per second (pps) and there is a single dominantsound source, which has an F0 of 200 Hz. As such, the modulating signals259L (mL) and 259R (mR) each have a period of 5 milliseconds (ms).Additionally, the dominant sound source is on the left side of therecipient's head (i.e., proximate to cochlear implant 202L), with an ITDat the right cochlear implant 202R of 250 microseconds (μs). As such,the pulses in the stimulation pulse sequence 268R delivered to therecipient's right-side cochlea by cochlear implant 202R are delayed by250 μs relative to the pulses in the stimulation pulse sequence 268Ldelivered to the recipient's left-side cochlea by cochlear implant 202L.In FIG. 3, the delay is labelled as “tR.”

In summary, FIGS. 2 and 3 illustrate embodiments in which cochlearimplants 202L and 202R generate stimulation pulse sequences 268L and268R, respectively, with a same amplitude modulation based on thefundamental frequency (F0) of the one or more sound sources 221 (i.e.,the cochlear implants 202L and 202R synchronize the modulation of thestimulation pulse amplitudes in the first and second pulse sequences268L and 268R). In FIG. 2, the same modulation applied at both of thecochlear implants 202L and 202R is based on the full ipsilateral and thefull contralateral audio data (i.e., based on the first set of soundsignals 248L and the second set of sound signals 248R), which isexchanged between the cochlear implants.

Additionally, in the embodiments of FIGS. 2 and 3, the cochlear implants202L and 202R are configured to synchronize, in time, the delivery ofthe stimulation pulse sequences 268L and 268R to the recipient based onthe relative location of the one or more sound sources 221. Again, therelative timing at which the stimulation pulse sequences 268L and 268Rare delivered to the recipient is determined based on the fullipsilateral and the full contralateral audio data (i.e., based on thefirst set of sound signals 248L and the second set of sound signals248R), which is exchanged between the cochlear implants. The relativetiming between the stimulation pulse sequences 268L and 268R correspondsto the ITD the first set of sound signals 248L and the second set ofsound signals 248R (i.e., the delay between the which the first set ofsound signals 248L and the second set of sound signals 248R are receivedat the cochlear implants 202L and 20R, or vice versa). As a result,bilateral cochlear implant system 200 is configured to both improvepitch perception (via the synchronized (the same) F0 amplitudemodulation) and to provide appropriate ITD cues (via the synchronizedtiming of the delivery of the stimulation pulse sequences 268L and 268Rto the recipient).

In certain embodiments of FIG. 2, the delay between the delivery of thestimulation pulse sequences 268L and 268R may directly correspond to thedetermined ITD. However, in certain embodiments, the ITD cues (relativedelay between delivery of the pulse sequences 268L and 268R) can beexaggerated, compensating for the reduced sensitivity of cochlearrecipients to ITD cues. For example, the relative delay between deliveryof the pulse sequences 268L and 268R may be larger than the estimatedITD, such as a multiple of the actual ITD (e.g., the pulse delay couldbe twice the estimated ITD).

Additionally or alternatively, the ILD cues could be exaggerated by themixers 256L or 256R by applying an additional gain or attenuation to themodulated envelopes 261L or 261R (v4L or v4R) on the appropriate side.That is, in such embodiments, the delay signals 267L and 267R are alsoapplied to the mixers 256L and 256R, respectively. As a result, themixers 256L or 256R can adjust the gain or attenuation applied to themodulated envelopes 261L or 261R based on the ITD (as represented in thedelay signals 267L and 267R).

As noted, FIG. 2 illustrates an embodiment in which the cochlearimplants 202L and 202R exchange the audio data 251L and 251R. FIG. 4illustrates an alternative embodiment in which signals, which are lowerbandwidth than the audio data 251L and 251R, are exchanged between twocochlear implants, in accordance with embodiments presented herein.

More specifically, shown in FIG. 4 is a cochlear implant system 400comprising a left (first) cochlear implant 402L and a right (second)cochlear implant 402R. Cochlear implant 402L is similar to cochlearimplant 202L and comprises a microphone array 250L (e.g.,dual-microphone system), a filterbank 252L, a smoother 254L, a mixer256L, a pulse generator 258L, and a modulation controller 260L. However,cochlear implant 402L also comprises a low-pass filter 470L.

Cochlear implant 402R is similar to cochlear implant 202R and comprisesa microphone array 250R (e.g., dual-microphone system), a filterbank252R, a smoother 254R, a mixer 256R, a pulse generator 258R, and amodulation controller 260R. However, cochlear implant 402R alsocomprises a low-pass filter 470R.

Unless noted below, components/blocks in FIG. 4 with similar numberingto components/blocks in FIG. 2 may perform a substantially similarfunction as the same similarly number component/block of FIG. 2.However, as detailed below, the components/blocks in FIG. 4 may operatebased on similar, but slightly different inputs, than the same similarlynumbered component/block of FIG. 2.

Moreover, unless noted below, signals and/or sets of signal sets withsimilar numbering to signals and/or sets of signal sets in FIG. 2 may besubstantially similar to the same similarly number signals and/or setsof signal sets of FIG. 2. However, as detailed below, the signals and/orsets of signals FIG. 4 may be generated based on similar, but slightlydifferent inputs, than the same similarly numbered signals and/or setsof signals of FIG. 2.

As noted above, acoustic sound signals (sounds) 248L are received at themicrophone array 250L, while acoustic sound signals (sounds) 248R arereceived at the microphone array 250L. The acoustic sound signals 248Land 248R are used to generate audio data (aL) 251L and 251R,respectively.

As described above with reference to FIG. 2, the audio data 251L and251R are applied to filterbanks 252L and 252R, respectively, whichgenerate filterbank envelopes 253L (v1L) and filterbank envelopes 253R(v1R), respectively. Similarly, the audio data 251L and 251R are appliedto the modulation controllers 260L and 260R, respectively.

In the specific example of FIG. 4, the audio data 251L and 251R are alsoapplied to the low-pass filters 470L and 470R, respectively. Theacoustic sound signal 251L is applied to the low-pass filter 470L togenerate a low-frequency audio data 471L. That is, low-frequency audiodata 471L represents only low frequency portion of the audio data 251L.Similarly, the audio data 251R is applied to the low-pass filter 470R togenerate low-frequency audio data 471R. That is, low-frequency audiodata 471R represents only a low frequency portion of the audio data251R.

FIG. 4 illustrates an example arrangement in which the low-pass filters470L and 470R are separate from the filterbanks 252L and 252R,respectively. However, in an alternative embodiment, the low-passfilters 470L and 470R may be implemented by collecting the outputs froma small number (e.g., 2, 3, or 4) of the lowest frequency band-passfilters in the filterbanks 252L and 252R, respectively. That is, theoutputs from a small number of the filterbanks 252L can be summed togenerate low-frequency audio data 471L, while a small number of thefilterbanks 252R can be summed to generate low-frequency audio data471R.

In the example of FIG. 4, cochlear implants 402L and 402R are configuredto operate a two-way audio link/channel 462 that enables the transfer oflow-frequency audio data 471L and 471R between the cochlear implants.That is, the two-way audio channel 462 enables the cochlear implant 402Rto send low-frequency audio data 471R to cochlear implant 402L and,similarly, enables cochlear implant 402L to send low-frequency audiodata 471L to cochlear implant 402R. The two-way audio channel 462 may bea digital wired electrical channel or a digital wireless channel (e.g.,a standardized wireless channel, such as Bluetooth®, Bluetooth® LowEnergy (BLE) or other channel interface making use of any number ofstandard wireless streaming protocols; a proprietary protocol forwireless streaming of the audio data; etc. Bluetooth® is a registeredtrademark owned by the Bluetooth® SIG).

As noted above, in the example of FIG. 2, the cochlear implants 202L and202R exchange the complete audio data 251L and 251R with one another. Incontrast, in the example of FIG. 4, the cochlear implants 402L and 402Ronly exchange a frequency-limited portion of the audio data 251L and251R with one another (i.e., low-frequency audio data 471L and 471R). Assuch, the low-frequency audio data 471L and 471R can be transmitteddigitally (e.g. wirelessly) using a lower data rate than the originalaudio data 251L and 251R, which has the benefit of reducing powerconsumption.

In FIG. 4, the audio data 251L and the low-frequency audio data 471R(received directed or received via the two-way audio channel 462) areapplied to each of the modulation controllers 260L and 260R. In general,the modulation controllers 260L and 260R operate, as described above, togenerate modulator signals 259L (mL) and 259R (mR), respectively, thateach have a period corresponding to the fundamental frequency (F0) ofthe most dominant harmonic component in the audio data 251L and 251R.That is, the modulation controllers 260L and 260R are each configured toidentify the fundamental frequency (F0) associated with received soundsignals 248L and 248R. The modulation controllers 260L and 260R thengenerate the modulation signals 259L and 259R, respectively, based onthe identified fundamental frequency (F0).

In the example of FIG. 4, the modulation controllers 260L and 260Roperate on both the ipsilateral (same side) audio data 251L and thecontralateral (other side) low-frequency audio data 471R or 472R(lower-bandwidth signals). In certain embodiments, modulation controller260L is configured to generate a first estimate of the fundamentalfrequency, referred to as “F0 _(iL),” using the ipsilateral audio data251L and a second estimate of the fundamental frequency, referred to as“F0 _(cL),” using the contralateral low-frequency audio data 471R. Ifthe two estimates F0 _(iL), and F0 _(cL) are approximately equal, thenit is assumed that there is one dominant sound source in theenvironment, and binaural processing functions in accordance withembodiments presented are enabled. Conversely, if the two estimates F0_(iL), and F0 _(cL) are significantly different, then it is assumed thatthere is not a single dominant sound source, and the binaural processingfunctions in accordance with embodiments presented herein disabled. Themodulation controller 260R may operate in a similar to manner togenerate and compare two estimates of the fundamental frequency,referred to as “F0 _(iR)” (made using the ipsilateral audio data 251R)and F0 _(cR)” (made using the contralateral low-frequency audio data471L).

The modulation controllers 260L and 260R will each reach the sameconclusion regarding whether or not to disable the binaural processingfunctions in accordance with embodiments presented are enabled. That is,the lower-bandwidth signals 471L and 471R still allows the common F0 andITD to be estimated by the modulation controllers 260L and 260R.

When not disabled, the cochlear implants 402L and 402R will each operateas described above with reference to FIG. 2 in order to generate thestimulation pulse sequences 268L and 268R, respectively. As above, thestimulation pulse sequences 268L and 268R are generated using the sameamplitude modulation (using the same modulation function corresponds toF0 of the one or more sound sources 221). However, depending on thelocation of the most dominant harmonic sound source, the stimulationpulses in either stimulation pulse sequence 268R or 268L may be timedelayed relative to the other, where the time delay is based on anestimate of the ITD for the most dominant harmonic sound source.

In summary, FIG. 4 illustrates an arrangement that is substantiallysimilar to that of FIG. 2. However, whereas in FIG. 2 the cochlearimplants 202L and 202R exchange the full audio data 251L and 251R, thecochlear implants 402L and 402R only exchange low-frequency portions ofthe audio data 251L and 251R. Thereafter, cochlear implants 402L and402R operate as described with reference to FIG. 2 in order to generatethe pulse sequences 268L and 268R delivered to the left and right ears,respectively, of the recipient.

As noted above, the embodiments of FIGS. 2 and 4 generally rely on thebi-directional exchange of audio data between the bilateral cochlearimplants. FIG. 5 illustrates another embodiment that does not rely upona bi-directional exchange of audio data. As described further below, thecochlear implants of FIG. 5 are each configured to derive asynchronization signal from the ipsilateral audio data only and use thissynchronization signal to control the pulse timing to preserve ITDinformation.

More specifically, FIG. 5 is a functional block diagram of a bilateralcochlear implant system 500 in accordance with embodiments presentedherein. As shown, the bilateral cochlear implant system 500 comprises aleft (first) cochlear implant 502L and a right (second) cochlear implant502R. Referring first to cochlear implant 502L, the cochlear implantcomprises a microphone array 550L (e.g., dual-microphone system), afilterbank 552L, a smoother 554L, a mixer 556L, a pulse generator 558L,and a modulation controller 560L.

In certain examples, the operations described below with reference tofilterbank 552L, smoother 554L, mixer 556L, and modulation controller560L may be performed at a processing module, such as processing module124L of FIG. 1D. Additionally, in certain examples, certain operationsdescribed below with reference to pulse generator 558L may be performedat a processing module (e.g., processing module 124L), while otheroperations may be performed at a stimulator unit, such as stimulatorunit 142L of FIG. 1D.

Cochlear implant 502R, which is substantially similar to cochlearimplant 502L, comprises a microphone array 5508, a filterbank 552R, asmoother 554R, a mixer 556R, a pulse generator 558R, and a modulationcontroller 560R. In certain examples, the operations described belowwith reference to filterbank 552R, smoother 554R, mixer 5568, andmodulation controller 560R may be performed at a processing module, suchas processing module 124R of FIG. 1E. Additionally, in certain examples,certain operations described below with reference to pulse generator558R may be performed at a processing module (e.g., processing module124R), while other operations may be performed at a stimulator unit,such as stimulator unit 142R of FIG. 1E.

Although FIG. 5 will be described with reference to the use ofmicrophone arrays 550L and 550R, it is to be appreciated that thecochlear implants 502L and 502R may also or alternatively includedifferent types and combinations of sound input devices. It is also tobe appreciated that the functional blocks shown in FIG. 5 for each ofcochlear implants 502L and 502 may be distributed across one, two, ormore different physical devices. For example, certain functional blocksshown in FIG. 5 for cochlear implant 502L may be part of an externalcomponent (e.g., external component 104L), while other functional blocksfor cochlear implant 502L may be part of an implantable component (e.g.,implantable component 112L). Alternatively, all of the functional blocksfor cochlear implant 502L may be part of an implantable component, thefunctional blocks for cochlear implant 502L may be split between twoexternal components and an implantable component, etc.

Returning to the example of FIG. 5, a first set of acoustic soundsignals (sounds) 548L are received at the microphone array 550L and areused to generate audio data (aL) 551L. More specifically, the audio data551L is derived from microphone signals, processed by analog-to-digitalconverters (ADC), a beamformer, and an Automatic Gain Control (AGC), allof which have been omitted from FIG. 5 for ease of illustration. Due, inpart, to the use of different stimulation channels to deliverstimulation to the recipient, the audio data 551L is applied to thefilterbank 552L, which comprises a band-pass filter and an envelopedetector for each of a plurality of stimulation channels. As such, thefilterbank 552L produces a set (e.g., a plurality) of filterbankenvelopes 553L (v1L), where each filterbank envelope is associated witha stimulation channel. In a similar manner, microphone array 550Rconverts a second set of acoustic sound signals (sounds) 548R are intoaudio data (aR) 551R.

Similar to the above embodiments, the lines/arrows marked by “/N” inFIG. 5, such as arrows 553L and 553R, indicate sets of related signals,with one signal for each of a plurality of stimulation channels in thecochlear implant system. A typical cochlear implant system may havebetween 12 and 22 stimulation channels, although other numbers ofchannels may be used in different embodiments.

The filterbank envelopes 553L and 553R are applied to the smoothers 554Land 554R, respectively, which smooth each of the filterbank envelopes toremove amplitude fluctuations having frequencies within and above anexpected range of fundamental frequencies. The smoothers 554L and 554Rproduce a set of smoothed envelope signals 555L (v3L) and 55R (v3R),respectively.

Additionally, the smoothers 554L and 554R delay the set of filterbankenvelopes 553L and 553R, respectively, to produce a set of delayedfilterbank envelopes 557L (v2L) and 557R (v2R), respectively, with adelay that matches the inherent delay that is introduced by thesmoothing operations of smoother 554L and 554R, respectively. In otherwords, envelopes 555L and 557L are aligned in time and the envelopes555R and 557R are aligned in time.

As noted elsewhere herein, the first set of acoustic sound signals 548Land the second set of acoustic sound signals 548R are generated by thesame one or more sound sources 521. As such, the set of acoustic soundsignals 548L and the second set of acoustic sound signals 548R arereceived “contemporaneously” (i.e., around the same time) by thecochlear implants 502L and 502R. However, the first set of acousticsound signals 548L and the second set of acoustic sound signals 548R arereceived at the respective cochlear implants 502L and 502R with arelative timing that corresponds to the location of the one or moresound sources 521. In other words, one of either the first or second setof acoustic sound signals may be received with a delay, relative to thereceipt of the other of first or second set of acoustic sound signals.The delay corresponds to the Interaural Time Difference (ITD) betweenthe left and right ears of the recipient, relative to the location ofthe one or more sound sources. The ITD may change (increase or decrease)as the location of the one or more sound sources 511 changes.

In the example of FIG. 5, the audio data 551L is also applied to themodulation controller 560L, while the audio data 55R is applied to themodulation controller 560R. In general, the modulation controllers 560Land 560R are each configured to generate a modulator signal 559L (mL)and 559R (mR) that each have a period corresponding to the fundamentalfrequency (F0) of the most dominant harmonic component in the audio data551L and 551R. That is, the modulation controller 560L is configured toidentify the fundamental frequency (F0) associated with received soundsignals 548L, while the modulation controller 560R is configured toidentify the fundamental frequency (F0) associated with received soundsignals 548R. The modulation controllers 560L and 560R then generate themodulation signals 559L and 559R, respectively, based on the identifiedfundamental frequency (F0).

In addition to generating modulator signals 559L and 559R, themodulation controllers 560L and 560R are each configured to generate anestimate, for each of the plurality of band-pass filter channels, of theprobability that the signal component in the corresponding band-passfilter channel is harmonically related to the dominant harmoniccomponent in the audio data 551L and 551R. As such, the modulationcontroller 560L generates a set 563L of harmonic probability signals(hL) and modulation controller 560R generates a set 563R of harmonicprobability signals (hR). Each signal in the sets 563L and 563Rcorrespond to one of the band-pass filter channels and provide anestimate of the probability that the signal in that correspondingband-pass filter channel is harmonically related to the dominantharmonic component in audio data 551L and 551R.

The sets 563L and 563R of harmonic probability signals are applied tothe mixers 556L and 556R, respectively. The mixer 556L is configured tosum the delayed filterbank envelopes 557L (v2L) and the modulatedenvelope signals 561L (v4L), with the relative proportions of eachcontrolled by the harmonic probability signals in set 561L. The mixer556L produces a set of output envelopes (v5L) 565L. The set of outputenvelopes 565L are then applied to the pulse generator 558L. Mixer 556Roperates in a similar manner to sum the delayed filterbank envelopes557R (v2R) and the modulated envelope signals 561R (v4R), with therelative proportions of each controlled by the harmonic probabilitysignals in set 561R. The mixer 556R produces a set 565R of modulatedoutput envelopes (v5R). The set 565R of modulated output envelopes arethen applied to the pulse generator 558R.

As noted above, the embodiments of FIGS. 2 and 4 each utilize an ITDestimator in the respective modulation controllers to estimate the ITDof the most dominant harmonic component in the ipsilateral andcontralateral audio data. However, in the embodiment of FIG. 5, thecochlear implants 502L and 502L operate using only the ipsilateral audiodata (e.g., the audio data received at the respective microphone arrays550L and 5508, respectively). As such, since the cochlear implants 502Land 502L do not have the contralateral audio data, the cochlear implants502L and 502L do not estimate the ITD directly from the audio data.Instead, in the embodiment of FIG. 5, the cochlear implants 502L and502L are each configured to derive a synchronization signal from theipsilateral audio data only and use this synchronization signal tocontrol the pulse timing to preserve ITD information.

Referring specifically to cochlear implant 502L, the modulationcontroller 560L includes an audio synchronizer 570L that generates asynchronization signal 571L (sL) from the audio data 551L. In accordancewith embodiments presented herein, the synchronization signal 571L goesactive at the start of each fundamental period of the modulation signal559L (i.e., once every T0 seconds, where T0=1/F0). The synchronizationsignal 571L is applied to the pulse generator 558L such that eachactivation of the synchronization signal 571L triggers the pulsegenerator 558L to generate a sequence of pulses of duration T0 and withthe modulation of F0, as described above. That is, synchronizationsignal 571L initiates the start of a sequence of F0 modulated pulses,where the sequence has a duration of T0.

The audio synchronizer 570L may use any of a number of different methodsto generate the synchronization signal 571L. FIGS. 6A-6C are blockdiagrams illustrating example methods that may be performed by thecochlear implant 502L (e.g., audio synchronizer 570L) to generate thesynchronization signal 571L.

Referring first to FIG. 6A, shown is a first embodiment for the audiosynchronizer 570L, referred to as audio synchronizer 670A, in which aband-pass filter 672A spanning a low frequency range (e.g., about 70 Hzto about 500 Hz) is applied to the audio data 551L (FIG. 5). Applicationof the band-pass filter 672A to the audio data 551L generates anauxiliary signal 673A that includes multiple harmonics of the dominantharmonic sound source. As a result, the envelope of the auxiliary signal673A will modulate at F0. As shown in FIG. 6A, an envelope detector 674Aapplies envelope detection to the auxiliary signal 673A to produce anauxiliary envelope signal 675A. A synchronization signal generator 676Athen derives the synchronization signal 571L (FIG. 5) from one or moreparticular attributes of the auxiliary envelope signal 675A. Forexample, in one embodiment, the synchronization signal generator 676Aderives the synchronization signal 571L from the positive peaks of theauxiliary envelope signal 675A. The peak detection process can utilizethe estimated F0, and hence the estimated period T0, to avoidspurious/false peaks. In an alternative example, the synchronizationsignal generator 676A derives the synchronization signal 571L from thenegative peaks (i.e. troughs) of the auxiliary envelope signal 675A.

In a still other embodiment, the synchronization signal generator 676Aincludes a high-pass filter having a low corner frequency (e.g., about50 Hz). In this embodiment, the high-pass filter is applied to theauxiliary envelope signal 675A to remove the low-frequency component ofthe envelope. The synchronization signal generator 676A may then detectand utilize positive zero-crossings and/or negative zero-crossings togenerate the synchronization signal 571L.

FIG. 6B illustrates another embodiment for the audio synchronizer 570L,referred to as audio synchronizer 670B, in which outputs (filterbankenvelopes) from a selected number (e.g., 2, 3, or 4) of the lowestfrequency band-pass filters in the filterbank 552L (FIG. 5) areobtained. In FIG. 6B, the filterbank envelopes from the selected numberof the lowest frequency band-pass filters in the filterbank 552L arerepresented by arrows 653(1)-665(N).

The filterbank envelopes 653(1)-665(N) are summed at summation module(summer) 678B to generate an auxiliary signal 673B that includesmultiple harmonics of the dominant harmonic sound source. As a result,the envelope of the auxiliary signal 673B will modulate at F0. As shownin FIG. 6B, an envelope detector 674B applies envelope detection to theauxiliary signal 673B to produce an auxiliary envelope signal 675B. Asynchronization signal generator 676B then derives the synchronizationsignal 571L (FIG. 5) from one or more signal attributes (one or moreattributes) of the auxiliary envelope signal 675B. In general, thesynchronization signal generator 676B may operate similarly tosynchronization signal generator 676A, described above with reference toFIG. 6A, to generate the synchronization signal 571L from one or moreattributes of the auxiliary envelope signal 675B (e.g., from thepositive peaks, the negative peaks, he positive zero-crossings, negativezero-crossings, etc.).

FIG. 6C illustrates another embodiment for the audio synchronizer 570L,referred to as audio synchronizer 670C, in which a variable band-passfilter 677C is applied to the audio data 551L (FIG. 5). The variableband-pass filter 677C has a center frequency is set to pass theestimated F0, and an upper cut-off frequency that is set to block afrequency of twice F0.

Application of the variable band-pass filter 677C to the audio data 551Lgenerates an auxiliary signal 673C that includes substantial energy fromthe fundamental component, but little energy from the higher harmonics.As shown in FIG. 6C, an envelope detector 674C applies envelopedetection to the auxiliary signal 673C to produce an auxiliary envelopesignal 675C. A synchronization signal generator 676C then derives thesynchronization signal 571L (FIG. 5) from one or more attributes of theauxiliary envelope signal 675C. In general, the synchronization signalgenerator 676C may operate similarly to synchronization signal generator676A, described above with reference to FIG. 6A, to generate thesynchronization signal 571L from one or more attributes of the auxiliaryenvelope signal 675C (e.g., from the positive peaks, the negative peaks,the positive zero-crossings, the negative zero-crossings, etc.).

Returning to the specific example of FIG. 5, the cochlear implant 502Ralso includes a modulation controller 560R with an audio synchronizer570R. The audio synchronizer 570R may operate, for example, as describedabove with reference to FIGS. 6A-6C to generates a synchronizationsignal 571R (sR) from the audio data 551R. In accordance withembodiments presented herein, the synchronization signal 571R goesactive at the start of each fundamental period of the modulation signal559R (i.e., once every T0 seconds, where T0=1/F0). The synchronizationsignal 571R is applied to the pulse generator 558R such that eachactivation of the synchronization signal 571R triggers the pulsegenerator 558R to generate a sequence of pulses of duration T0 and withthe modulation of F0, as described above. That is, synchronizationsignal 571R initiates the start of a sequence of F0 modulated pulses,where the sequence has a duration of T0.

In the embodiment of FIG. 5, in response to a harmonic audio source inthe audio environment, the bilateral cochlear implant system 500 willobtain audio data 551L at the left ear and audio data 551R at the rightear, whereby the corresponding harmonic components of the audio data551L and 551R will have an ITD that is dependent on the location of theaudio source. Because, as detailed above, the timing of eachsynchronization signal 571L and 571R is directly related to the temporalfeatures of the dominant harmonic component in the corresponding audiodata 551L and 5518, the same ITD will be present between thesynchronization signals 571L and 571R, and thus also between the pulsessequence 568L delivered via the left cochlear implant 502L, and thepulse sequence 568R delivered via the right cochlear implant 502R.

That is, as noted above, the synchronization signals 571L and 571R areactivated (generated) based on the same parameters of the audio data551L and 551R. These parameters will occur in 551L and 551R with arelative time difference that corresponds to the ITD. For example, ifthe dominant sound source is on the left, the features will appear in551L before the same features appear in 551R. The time period betweenwhen the features occur in 551L and when the features appear in 551Rcorresponds to the ITD. Therefore, since the synchronization signals571L and 571R are activated based on these features (which are appear in551R after 551L at a time delay corresponding to the ITD), then thesynchronization signal 571R will also be activated a time period aftersynchronization signal 571L, where the delay between signals 571L and571R corresponds to the ITD. Again, since the synchronization signals571L and 571R control when pulses in the pulses sequences 568L and 568Rwill be generated, each group of pulses generated at 558R will bedelayed relative to each group of pulses generated at 558L, at leastuntil the ITD of the input audio changes. The result again is pulsesequences such as those shown in FIG. 3.

In summary, FIGS. 5 and 6A-6C illustrate embodiments in which cochlearimplants 502L and 502R generate stimulation pulse sequences 568L and568R, respectively, with an amplitude modulation that is based on thefundamental frequency (F0) of the one or more sound sources 521 (i.e.,the cochlear implants 502L and 502R synchronize the modulation of thestimulation pulse amplitudes in the first and second pulse sequences568L and 568R). In FIG. 5, the modulation applied at both of thecochlear implants 502L and 502R is based on the ipsilateral audio dataonly (i.e., based on only the first set of sound signals 548L atcochlear implant 502L and based on only the second set of sound signals548R at cochlear implant 502R).

Additionally, in the embodiments of FIGS. 5 and 6A-6C, the cochlearimplants 502L and 502R are configured to synchronize, in time, thedelivery of the stimulation pulse sequences 568L and 568R to therecipient based on the relative location of the one or more soundsources 521. Again, the relative timing at which the stimulation pulsesequences 568L and 568R (i.e., time delay between delivery of the pulsesequences) is determined from the ipsilateral audio data only (i.e.,based on only the first set of sound signals 548L at cochlear implant502L and based on only the second set of sound signals 548R at cochlearimplant 502R). In particular, each of the cochlear implants 502L and502R synchronize the timing of the delivery of the stimulation pulsesequences 568L and 568R to the recipient based on one or more attributesoccurring in both of the first and second sets of sound signals 548L and548R, wherein the one or more attributes occur in the first and secondsets of sound signals 548L and 548R with a relative timing correspondingto the ITD (i.e., the one or more attributes may be delayed in one ofthe first or second sets of sound signals 548L and 548R relative to theother of the first or second sets of sound signals 548L and 548R). As aresult, the relative timing between the delivery of the stimulationpulse sequences 568L and 568R corresponds to the ITD the first set ofsound signals 548L and the second set of sound signals 548R (i.e., thedelay between the which the first set of sound signals 548L and thesecond set of sound signals 548R are received at the cochlear implants502L and 50R, or vice versa). As a result, bilateral cochlear implantsystem 500 is configured to both improve pitch perception (via thesynchronized (the same) F0 amplitude modulation) and to provideappropriate ITD cues (via the synchronized timing of the delivery of thestimulation pulse sequences 568L and 568R to the recipient).

FIG. 7 is a flowchart of a method 780 in accordance with certainembodiments presented herein. Method 780 begins at 781 where a firstcochlear implant of a bilateral cochlear implant system receives a firstset of sound signals. At 782, a second cochlear implant of the bilateralcochlear implant system receives a second set of sound signals, whereinthe first set of sound signals and the second set of sound signals areassociated with a same one or more sound sources. At 783, the firstcochlear implant generates a first sequence of stimulation pulses basedon the first set of sound signals, wherein the first sequence ofstimulation pulses have amplitudes that are modulated with a firstmodulation. At 784, the first cochlear implant delivers the firstsequence of stimulation pulses to a first ear of a recipient of thebilateral cochlear implant system. At 785, the second cochlear implantgenerates a second sequence of stimulation pulses based on the secondset of sound signals, wherein the second sequence of stimulation pulseshave amplitudes that are modulated using the same first modulation asthe first sequence of stimulation pulses. At 786, the second cochlearimplant delivers the second sequence of stimulation pulses to a secondear of the recipient. The second sequence of stimulation pulses isdelivered to the recipient with a time delay relative to delivery of thefirst sequence of stimulation pulses and wherein the time delay is basedon an Interaural Time Difference (ITD) associated with receipt of thefirst set of sound signals at the first cochlear implant and receipt ofthe second set of sound signals at the second cochlear implant.

FIG. 8 is a flowchart of a method 890 in accordance with certainembodiments presented herein. Method 890 begins at 891 where a firstcochlear implant of a bilateral cochlear implant system receives firstaudio data (e.g., a first set of sound signals). At 892, the secondcochlear implant of the receives second audio data (e.g., a second setof sound signals) at a second cochlear implant of the bilateral cochlearimplant system, wherein the first and second audio data are associatedwith a same fundamental frequency. At 893, the first cochlear implantgenerates a first sequence of stimulation pulses representative of thefirst audio data and, at 894, the first cochlear implant amplitudemodulates the first sequence of stimulation pulses based on thefundamental frequency of the first audio data and second audio data. At895, the second cochlear implant generates a second sequence ofstimulation pulses representative of the second audio data and, at 896,the second cochlear implant amplitude modulates the second sequence ofstimulation pulses based on the fundamental frequency of the first audiodata and second audio data. At 897, a timing of delivery of the firstsequence of stimulation pulses to a first ear of a recipient of thebilateral cochlear implant system is synchronized with a timing ofdelivery of the second sequence of stimulation pulses to a second ear ofthe recipient of the bilateral cochlear implant system.

Merely for ease of description, the techniques presented herein haveprimarily described herein with reference to an illustrative medicaldevice system, namely a bilateral cochlear implant system that deliverselectrical stimulation to both ears of a recipient. However, it is to beappreciated that the techniques presented herein may also be used with avariety of other medical devices that, while providing a wide range oftherapeutic benefits to recipients, patients, or other users, maybenefit from the techniques presented. For example, a bilateral cochlearimplant system in accordance with embodiments presented herein may alsodeliver acoustic stimulation to one or both ears of the recipient (e.g.,one or more of the cochlear implants is an electro-acoustic cochlearimplant). It is also to be appreciated that the two cochlear implants ofa bilateral cochlear implant system in accordance with embodimentspresented need not be identical with respect to, for example, the numberof electrodes used to electrically stimulate the cochlea, the type ofstimulation delivered, etc. Furthermore, it is to be appreciated thatthe techniques presented herein may be used with other binaural hearingprosthesis systems, such as systems including acoustic hearing aids,bone conduction devices, middle ear auditory prostheses, direct acousticstimulators, other electrically simulating auditory prostheses (e.g.,auditory brain stimulators), etc. The techniques presented herein mayalso be used with vestibular devices (e.g., vestibular implants), visualdevices (i.e., bionic eyes), sensors, pacemakers, drug delivery systems,defibrillators, functional electrical stimulation devices, catheters,seizure devices (e.g., devices for monitoring and/or treating epilepticevents), sleep apnea devices, electroporation, etc.

It is to be appreciated that the above embodiments are not mutuallyexclusive and may be combined with one another in various arrangements.

The invention described and claimed herein is not to be limited in scopeby the specific preferred embodiments herein disclosed, since theseembodiments are intended as illustrations, and not limitations, ofseveral aspects of the invention. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the invention in addition to those shown and describedherein will become apparent to those skilled in the art from theforegoing description. Such modifications are also intended to fallwithin the scope of the appended claims.

1. A method, comprising: receiving first audio data at a first cochlearimplant of a bilateral cochlear implant system; receiving second audiodata at a second cochlear implant of the bilateral cochlear implantsystem, wherein the first and second audio data are associated with asame fundamental frequency; generating, at the first cochlear implant, afirst sequence of stimulation pulses representative of the first audiodata; amplitude modulating the first sequence of stimulation pulsesbased on the fundamental frequency of the first audio data and secondaudio data; generating, at the second cochlear implant, a secondsequence of stimulation pulses representative of the second audio data;amplitude modulating the second sequence of stimulation pulses based onthe fundamental frequency of the first audio data and second audio data;and synchronizing a timing of delivery of the first sequence ofstimulation pulses to a first ear of a recipient of the bilateralcochlear implant system with a timing of delivery of the second sequenceof stimulation pulses to a second ear of the recipient of the bilateralcochlear implant system.
 2. The method of claim 1, wherein thefundamental frequency is related to one or more sound sources in anaudio environment of the recipient, and wherein synchronizing the timingof delivery of the first sequence of stimulation pulses with the timingof delivery of the second sequence of stimulation pulses comprises:synchronizing the timing of the delivery of the first sequence ofstimulation pulses to the first ear of the recipient with the timing ofdelivery of the second sequence of stimulation pulses to the second earof the recipient based on a relative location of the one or more soundsources in the audio environment.
 3. The method of claim 1, whereinsynchronizing the timing of delivery of the first sequence ofstimulation pulses with the timing of delivery of the second sequence ofstimulation pulses comprises: synchronizing the timing of the deliveryof the first sequence of stimulation pulses and the second sequence ofstimulation pulses based on one or more signal attributes occurring inboth of the first audio data and the second audio data.
 4. The method ofclaim 3, wherein the one or more signal attributes occur in the firstaudio data and the second audio data with a relative timingcorresponding to an Interaural Time Difference (ITD) associated withreceipt of the first audio data at the first cochlear implant andreceipt of the second audio data at the second cochlear implant.
 5. Themethod of claim 3, further comprising: detecting, at the first cochlearimplant, one or more signal attributes of the first audio data;detecting, at the second cochlear implant, one or more signal attributesof the second audio data, wherein the one or more signal attributes ofthe second audio data are the same one or more signal attributes of thefirst audio data; setting a timing of the delivery of the first sequenceof stimulation pulses to the first ear of the recipient based on atiming of the one or more signal attributes in the first audio data; andsetting a timing of the delivery of the second sequence of stimulationpulses to the second ear of the recipient based on a timing of the oneor more signal attributes in the second audio data.
 6. The method ofclaim 1, wherein synchronizing the timing of delivery of the firstsequence of stimulation pulses to the first ear of the recipient withthe timing of delivery of the second sequence of stimulation pulses tothe second ear of the recipient comprises: delivering the secondsequence of stimulation pulses to the second ear of the recipient with atime delay, relative to delivery of the first sequence of stimulationpulses to the first ear of the recipient.
 7. The method of claim 6,wherein the time delay for delivery of the second sequence ofstimulation pulses relative to the delivery of the first sequence ofstimulation pulses is substantially equal to an Interaural TimeDifference (ITD) associated with receipt of a first audio data at thefirst cochlear implant and receipt of the second audio data at thesecond cochlear implant, respectively.
 8. The method of claim 7, furthercomprising: determining the timing of the delivery of the secondsequence of stimulation pulses based only on the second audio data. 9.The method of claim 8, further comprising: detecting one or more signalattributes of the second audio data that also occur in the first audiodata; and timing the delivery of the second sequence of stimulationpulses to the second ear of the recipient based on a timing of the oneor more signal attributes in the second audio data, wherein the firstcochlear implant is configured to time delivery of the first sequence ofstimulation pulses based on a timing of the one or more signalattributes in the first audio data.
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 15. A method, comprising:receiving a first set of sound signals at a first implant of a bilateralimplant system; receiving a second set of sound signals at a secondimplant of the bilateral implant system, wherein the first set of soundsignals and the second set of sound signals are associated with a sameone or more sound sources; generating, at the first implant, a firstsequence of stimulation pulses based on the first set of sound signals,wherein the first sequence of stimulation pulses have amplitudes thatare modulated with a first modulation; delivering the first sequence ofstimulation pulses to a first ear of a recipient of the bilateralimplant system; generating, at the second implant, a second sequence ofstimulation pulses based on the second set of sound signals, wherein thesecond sequence of stimulation pulses have amplitudes that are modulatedusing the same first modulation as the first sequence of stimulationpulses; and delivering the second sequence of stimulation pulses to asecond ear of the recipient, wherein the second sequence of stimulationpulses is delivered to the recipient with a time delay relative todelivery of the first sequence of stimulation pulses and wherein thetime delay is based on an Interaural Time Difference (ITD) associatedwith receipt of the first set of sound signals at the first implant andreceipt of the second set of sound signals at the second implant. 16.The method of claim 15, further comprising: sending first audio datafrom the first implant to the second implant, wherein the first audiodata is generated from the first set of sound signals; and sendingsecond audio data from the second implant to the first implant, whereinthe second audio data is generated the second set of sound signals. 17.The method of claim 16, further comprising: determining, at the firstimplant, the first modulation from the first set of sound signals andthe second audio data; and determining, at the second implant, the firstmodulation from the second set of sound signals and the first audiodata.
 18. The method of claim 16, wherein sending the first audio datafrom the first implant to the second implant comprises: converting thefirst set of sound signals into the first audio data, and sending thefirst audio data to the second implant; and wherein sending the secondaudio data from the second implant to the first implant comprises:converting the second set of sound signals into second audio data, andsending the second audio data to the first implant.
 19. The method ofclaim 16, wherein sending the first audio data from the first implant tothe second implant comprises: converting the first set of sound signalsinto first audio data, filtering the first audio data to generate afrequency limited first audio data, and sending only the frequencylimited first audio data to the second implant; and wherein sending thesecond audio data from the second implant to the first implantcomprises: converting the second set of sound signals into second audiodata, filtering the second audio data to generate a frequency limitedsecond audio data, and sending only the frequency limited second audiodata to the first implant.
 20. The method of claim 19: wherein filteringthe first audio data to generate a frequency limited first audio datacomprises: low-pass filtering the first audio data to generatelow-frequency first audio data representing only a low frequency portionof the first audio data; and wherein filtering the second audio data togenerate a frequency limited second audio data comprises: low-passfiltering the second audio data to generate low-frequency second audiodata representing only a low frequency portion of the second audio data.21. The method of claim 19: wherein filtering the first audio data togenerate a frequency limited first audio data comprises: applying thefirst audio data to a first filterbank configured to generate aplurality of filtered first output signals, and summing only a subset ofthe filtered first output signals to generate the frequency limitedfirst audio data, wherein filtering the second audio data to generate afrequency limited second audio data comprises: applying the second audiodata to a second filterbank configured to generate a plurality offiltered second output signals, and summing only a subset of thefiltered second output signals to generate the frequency limited secondaudio data.
 22. The method of claim 16, further comprising: determining,at the second implant, the time delay for delivery of the secondsequence of stimulation pulses relative to the delivery of the firstsequence of stimulation pulses based on the second set of sound signalsand the first audio data.
 23. The method of claim 22, whereindetermining the time delay for delivery of the second sequence ofstimulation pulses relative to the delivery of the first sequence ofstimulation pulses based on the second set of sound signals and thefirst audio data comprises: determining, at the second implant, an ITDof a most dominant harmonic component in each of the second set of soundsignals and the first audio data.
 24. The method of claim 15, whereinthe time delay for delivery of the second sequence of stimulation pulsesrelative to the delivery of the first sequence of stimulation pulses issubstantially equal to the ITD.
 25. The method of claim 15, wherein thetime delay for delivery of the second sequence of stimulation pulsesrelative to the delivery of the first sequence of stimulation pulses isgreater than the ITD.
 26. The method of claim 15, where generating, atthe first implant, a first sequence of stimulation pulses based on thefirst set of sound signals, wherein the first sequence of stimulationpulses have amplitudes that are modulated with a first modulation,comprises: applying the first set of sound signals to a first filterbankcomprising a band-pass filter and an envelope detector for each of aplurality of stimulation channels to produce a plurality of filterbankenvelopes, where each filterbank envelope is associated with astimulation channel; determining a fundamental frequency of the firstset of sound signals; generating, based on the fundamental frequency ofthe first set of sound signals, a set of modulated output envelopes fromthe plurality of filterbank envelopes; selecting a plurality ofmodulated output envelopes from the set of modulated output envelopes;and generating the first sequence of stimulation pulses based on theplurality of modulated output envelopes.
 27. The method of claim 26,further comprising: determining a harmonicity of each of the pluralityof filterbank envelopes; and generating, based on the fundamentalfrequency of the first set of sound signals, the set of modulated outputenvelopes from the plurality of filterbank envelopes based on thefundamental frequency of the first set of sound signals and theharmonicity of each of the plurality of filterbank envelopes.
 28. Themethod of claim 27, further comprising: prior to generating the set ofmodulated output envelopes from the plurality of filterbank envelopes,smoothing the plurality of filterbank envelopes.
 29. A implant system,comprising: a first implant configured to: receive a first set of soundsignals generated by at least one sound source, convert the first set ofsound signals into a first stimulation pulse train, wherein the firststimulation pulse train is artificially amplitude modulated based on afundamental frequency associated with the at least one sound source, anddeliver the first stimulation pulse train to a first ear of a recipientof the implant system; and a second implant configured to: receive asecond set of sound signals generated by the at least one sound source,convert the second set of sound signals into a second stimulation pulsetrain, wherein the second stimulation pulse train is artificiallyamplitude modulated based on the fundamental frequency associated withthe at least one sound source, determine, relative to delivery of thefirst stimulation pulse train to the first ear of the recipient, a timedelay for delivery of the second stimulation pulse train to a second earof the recipient, and deliver the second stimulation pulse train to thesecond ear of the recipient at a time corresponding to the time delay.30. The implant system of claim 29, wherein to determine the time delayfor delivery of the second stimulation pulse train to a second ear ofthe recipient, the second implant is configured to: determine the timedelay from an Interaural Time Difference (ITD) associated with receiptof the first set of sound signals at the first implant and receipt ofthe second set of sound signals at the second implant.
 31. The implantsystem of claim 30, wherein the time delay for delivery of the secondstimulation pulse train relative to the delivery of the firststimulation pulse train is substantially equal to the ITD.
 32. Theimplant system of claim 30, wherein the time delay for delivery of thesecond stimulation pulse train relative to the delivery of the firststimulation pulse train is greater than the ITD.
 33. The implant systemof claim 29: wherein the first implant is configured to send first audiodata to the second implant, wherein the first audio data is generatedfrom the first set of sound signals; and wherein the second implant isconfigured to send second audio data to the first implant, wherein thesecond audio data is generated the second set of sound signals.
 34. Theimplant system of claim 33, wherein the second implant is configured todetermine the time delay for delivery of the second stimulation pulsetrain relative to the delivery of the first stimulation pulse trainbased on the second set of sound signals and the first audio data. 35.(canceled)
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 45. Non-transitory computer readable storage media encodedwith instructions that, when executed by one or more processors, causethe one or more processors to: generate, at a first device, a firstsequence of stimulation pulses representative of first audio datareceived at the first device; generate, at a second device, a secondsequence of stimulation pulses representative of second audio datareceived at the second device; modulate the first sequence ofstimulation pulses based on one or more features of the first audio dataand the second audio data; modulate the second sequence of stimulationpulses based on the one or more features of the first audio data and thesecond audio data; and synchronize a timing of delivery of the firstsequence of stimulation pulses to a first ear of a recipient with atiming of delivery of the second sequence of stimulation pulses to asecond ear of the recipient.
 46. The non-transitory computer readablestorage media of 45, wherein the one or more features of the first audiodata and the second audio data comprise a frequency of the first audiodata and the second audio data.
 47. The non-transitory computer readablestorage media of claim 46, wherein the frequency is a fundamentalfrequency related to one or more sound sources in an audio environment,and wherein the instructions to synchronize the timing of delivery ofthe first sequence of stimulation pulses with the timing of delivery ofthe second sequence of stimulation pulses comprise instructions that,when executed by the one or more processors, cause the one or moreprocessors to: synchronize the timing of the delivery of the firstsequence of stimulation pulses to a first ear of a recipient with thetiming of delivery of the second sequence of stimulation pulses to asecond ear of the recipient based on a relative location of the one ormore sound sources in the audio environment.
 48. The non-transitorycomputer readable storage media of claim 45, wherein the instructions tosynchronize the timing of delivery of the first sequence of stimulationpulses with the timing of delivery of the second sequence of stimulationpulses comprise instructions that, when executed by the one or moreprocessors, cause the one or more processors to: synchronize the timingof the delivery of the first sequence of stimulation pulses and thesecond sequence of stimulation pulses based on one or more signalattributes occurring in both of the first audio data and the secondaudio data.
 49. The non-transitory computer readable storage media ofclaim 48, wherein the one or more signal attributes occur in the firstaudio data and the second audio data with a relative timingcorresponding to an Interaural Time Difference (ITD) associated withreceipt of the first audio data at the first device and receipt of thesecond audio data at the second device.